David and Goliath

Menu

Sunbursts at Timber Lakes………

This photo was taken at Timber Lakes a private development right next to the Wasatch National Park just east of Heber City, Utah. It was a crisp spring day with temperatures in the low 60’s. There was approximately 3 feet of snow on the ground. I opened up the sunroof and took this photograph of the towering pine trees with the aspen trees still waiting to break bud. The sun shone overhead and it was a blissful day. I love natural sunbursts in photography. I am always pleased when I can share a photo with this effect. I found this article that is very informative as it describes exactly how diffraction occurs. Read the article and then go and take a photograph with the sunburst. It is always fun to stretch and challenge yourself in photography.

Diffraction is a phenomenon that involves the modification of waves (direction and speed) caused when those waves pass through a narrow opening or past the edge of an object. When waves pass by an object, their direction is altered. When passing through a small opening, the same thing happens, with the end result being the spreading of the wave pattern. The term is applied to light, sound waves, and other types of waves (water, for example), as wave physics are similar through different media.

If the light passes through a perfectly circular opening, a small diffractive disc is created—the Fraunhofer diffraction pattern (named in honor of German optician Joseph von Fraunhofer). Instead of a point of light, you will see a small disc surrounded by a number of faint rings known as the Airy Disc (named after Sir George Airy, England’s Astronomer Royal from 1835-1881).

In photography, diffraction occurs when light waves pass through the diaphragm of a lens. It is most pronounced when the opening of the aperture diaphragm is constricted. Many photographers mistakenly believe that they get maximum sharpness at minimum aperture openings. In reality, the image gets softer because of the diffraction of the light. Because of this, diffraction gets a bad rap in the photo world, but it is diffraction that causes the star effect.

Ideal Airy disc for

resolving a single point of light

Diffracted light causes discs to

overlap, resulting in softer unresolved imagery

Tip 1: Safety first

If photographing with the sun in the frame, be sure to protect both your eyes and camera. Pointing a camera directly at the sun can be very dangerous for your eyes. In general, to get the star effect, the sun will be off-axis, but, when composing, take care to not swing the lens directly at the sun. If the scene is still too bright for a DSLR viewfinder, try the live view mode, if available.

Not only can the light be bad for your eyes, it can be bad for your camera. Identical to the principle used to burn leaves with a magnifying glass, focused bright sunlight from a camera lens, especially a telephoto lens, can damage the internal components of a DSLR or damage the sensor of a mirrorless or point-and-shoot camera. Be careful!

Lens and Aperture It is the phenomenon of diffraction that creates the star effect on distant single-point light sources and, sometimes, on specular highlights on an object in the frame. The size, shape, and characteristics of the star effect are a function of the size of the aperture opening (diffraction of light passing through an opening) and the number of aperture blades on the aperture diaphragm (diffraction of light passing an object).

The design of the aperture diaphragm has a profound effect on the star effect. Sometimes, your gear isn’t critical to a successful image, but when you are dealing with star effects, you will find that lenses have vastly different characteristics when it comes to this type of diffraction.

If the aperture blades form a perfect circle, you will not get the star effect and you will, instead, have distant highlights producing Airy Discs on your image. In general, the circles emanating from the disc will be so small and faint, depending on the light source’s distance and intensity, that you will not see the rings. Several modern lenses feature “rounded aperture blades” to help form a circle for the light to pass through.

Tip 2: Use smaller apertures

When it comes to star effects, in general, the smaller the aperture, the more pronounced the effect will be (there are other considerations that I will discuss later). However, just as you are increasing the diffractive effect from distant light sources, you will also be increasing diffraction throughout the image. There is a trade-off.

When the aperture diaphragm forms a polygon instead of a circle, we get the star effect. The light streaks or star points of the effect extend from the vertices of the polygon formed by the blades.

This is where it gets cool. With diaphragms that form a polygon, if you have an even number of aperture blades, you will get one point per blade extending from the vertex of each intersecting blade. The light streak will continue across the opening where it intersects the opposite vertex. Therefore, an even number of blades creates one star point per blade. A 6-blade aperture produces a star effect with 6 spikes.

If you have an aperture with an odd number of blades, the diffraction extends from the vertex across the opening where it does not intersect with another vertex. Therefore, an odd number of blades create two star points per blade. A 7-blade aperture produces a star effect with 14 spikes.

Tip 3: Know your lenses

Experimentation with your lenses will help you determine the ideal star effect f/stop. If you are on a star-effect mission, spend time with all your lenses and figure out which ones produce the best star effect. Then, if you are planning an image where you want your strongest star effects, break out that lens. Or, if you want to avoid it (star effects are not for everyone), use the lenses that tend to not make the effect.

One other thing with the lens that affects the start effect is the ability of the lens to handle flare. The better the optical formula and multi-coatings are able to reduce lens flare, the sharper your star effects will be. If the lens is incompetent when it comes to dealing with flare, you will see softer, less defined star effects.

Tip 4: Beware of filter flare

Sometimes flare can be caused by your UV filter. If you aren’t getting the star effects you desire, or if you are getting other flare, try removing the filter to see if it has a positive effect on your images.

Telescopes are designed to maximize the amount of light captured by the optical tube. Because of this, they don’t usually have aperture diaphragms. So then, why do we get the star effect in images from optical telescopes?

The star effect is created when the light passes by the secondary mirror that lives inside the tube of a reflecting Newtonian or Cassegrain telescope. That mirror is suspended inside the optical tube by struts and the number of struts creates an associated number of star points. 3 struts produce a 6-point star. 4 points render a 4-point star.

A detailed investigation of images from the famous orbiting Hubble Space Telescope shows that the scope is equipped with 4 struts to support its interior mirror.

Considerations

Day versus night Star effects exist in both daytime and nighttime photography. The star closest to Earth, the Sun, can give you great star effects during the day, as can the sun’s reflection from shiny objects and windows. At night, bright, distant light sources can produce the star effect. One bright, distant source of reflected light is the moon. With a wide-angle lens, you can get some great star effects from Earth’s natural satellite, too.

Exposure Your exposure affects the intensity of the star effect. The longer the exposure, the more star effect you will see, until the point at which the entire image is overexposed. The brighter the highlights in a photo, the more star effect.

In night photography, burning out highlights, such as street lamps and other artificial light sources, is sometimes unavoidable. The amount you let those highlights burn is directly related to the size and intensity of the star effect. How much you see of the star effects is dependent on the contrast in the scene.

Tip 5: Watch for other flare

Bright light sources that are entering the lens from the main axis can produce undesirable lens flare. Often, you can see this through the viewfinder when you compose the image. Not all lens flare is bad, and not all of it needs to be avoided, but you should be conscious of it so that you can take steps to remove or manage it in the frame.

Contrast Contrast plays a big role in how your star effects stand out. If a distant lamppost, surrounded by an ink-black sky, is creating your image highlights, you might get some great definition and an eye-popping star. If that light source has a relatively bright area behind it, you will lose some of your star effect.

The sun, if hanging in a low-contrast, bright sky, will produce less of a star effect than if in a deeper blue sky.

Tip 6: Mask the light

During the day, you will find that partially blocking the light from the sun will help give you a more dramatic star effect. This is because, by blocking part of the light source using trees, buildings, or other objects, you will increase the contrast in that region of the frame and make the star effect more pronounced.

Do this with your own eyes (don’t stare directly at the sun). Shade a portion of the sun with a building or tree and, through your peripheral vision, note that your eye produces star effects too! This is caused by the fact that nature did not give our eyes a perfectly circular iris.

Subject-to-lens distance The closer you are to the light that is producing the star effect, the larger the star effect will be in your frame. In fact, you can use the relative sizes of the star effects to illustrate depth. For example, the Brooklyn Bridge images in this article show star effects on the more distant Manhattan Bridge and Manhattan skyline that help reinforce the depth of the image.

Focal length Focal length is not directly related to the size of the star effects that you can create. If you change from a wide-angle lens to a telephoto lens, you might amplify the size of the star effects, but this is more of a function of getting “closer” to the subject versus an effect created by the lens itself. Of course, some lenses lend themselves to producing better star effects and some lenses, regardless of focal length will not produce crisp stars.

On a zoom lens, you can change the size of your star effects by zooming in or out, but the relative size and shape should not change drastically, as you are sending light through the same aperture.

You can make the star effects larger by zooming in or moving closer, but you cannot enlarge them in a given image without changing aperture.

Quality of Light As with all aspects of photography, the quality of light has an impact on your image. Star effects are no exception. Haze, smoke, fog, etc., can serve to reduce the sharpness of the effect. The relative size and brightness of the light source has an effect as well. Smaller and brighter works best. Obscuration of the light will either make (see Contrast, above) or break your star effect, so be prepared to reposition your camera to capture the best angle for the effect.

Filters and Post Processing If your lens is not producing the star-points effect you want it to, you can artificially create this effect by adding a “Star Effect” filter to your lens (hence my decision to call the phenomenon by this name) or create the effect in post processing with some image-editing software.

Star Effect Filters are etched in a crisscross pattern and are designed to intentionally diffract light and create the star point effect. They also create some rainbow dispersion effects and generally soften the overall image. Star effect filters come in all common lens thread sizes and have varying designs that produce star effects of different numbers of points (2 to 16), different point patterns (for example: North Star, streak, vector), different color streaks. B&H Photo currently has more than 800 variations. Check them out and use them to give your photos a creative twist.

You can also add the star effect in Photoshop and other editing software. As with most things in digital editing, there is a plethora of ways to do this, so scan the Internet for the star effect/starburst/sun star tutorial that works best for your image.

Starry, starry nights (and days) Love them or hate them? Cool trick or cheesy distraction? Share your thoughts and tips and tricks for either making more dramatic star effects, or avoiding them all together! Thanks for reading!